Low Airspeed Sensor
The Low Airspeed Sensor (LAS) is a sensor under research and development for measuring true airspeed for helicopters, especially below 30 knots. There are several safety-critical issues, e.g. loss of tail rotor effectiveness (LTE), in the low speed regime for helicopters. The accuracy of conventional airspeed systems, i.e. Pitot-static based airspeed systems, begin to degrade below 40 knots and are greatly affected by helicopter downwash.
Here are a few advantages of the LAS:
- high accuracy (< 0.1 knot)
- fast response (< 100 ms)
- low weight (< 2 oz.)
- small size (< 6.5" long, 2.9" wide, 3.5" high)
- virtual immune to EMI/RFI
- no Air Data Computer (ADC) required
Bell Helicopter flight-tested and compared the LAS to other airspeed sensors, i.e. Pitot-static, ultrasonic and laser. The LAS was able to distinguish between the airspeed and rotor frequency from the downwash all the way down to zero speed, while the other airspeed sensors failed to work below 30 knots showing erroneous speeds instead. Tao Systems and Bell Helicopter jointly published and presented the research flight test results at the 59th American Helicopter Society Forum.
The LAS can be optimized for custom speed ranges, reduced in size and weight, and ruggedized for certain environments. At this time, the LAS is undergoing research testing.
Here are a few other applications of the LAS:
- Unmanned Combat Armed Rotorcraft (UCAR) Air Data System
- Unmanned Combat Aerial Vehicle (UAV) Air Data System
- High Altitude Long Endurance (HALE) Vehicle Air Data System
- High Altitude Airship (HAA) Air Data System
- Aircraft Carrier Wind Speed
- Mangalam, S. M., Sarma, G. R., Augustin, M., and Yeary, D.: "Low Speed/Low Cost Airspeed Sensor for Helicopters," 59th American Helicopter Society Forum, Phoenix, AZ, May 2003.
- Mangalam, S. M.: "Phenomena-based Real-time Aerodynamic Measurement (PRAM) System for Aircraft Performance, Safety, and Control." IEEE Aerospace Conference, Big Sky, MT, March 2003.